Shape Phase Transition of the Axially Symmetric States Between the U(5) and SU(3) Symmetries

The shape phase structure and its transition of the nucleus in the transitional region between the U(5) and SU(3) symmetries is restudied within the framework of coherent-state theory with angular momentum projection in IBM-1. The certain angular momentum (or rotation-driven) effect on the nuclear shape is discussed. A coexistence of prolate and oblate shapes is found for the ground states of the transitional nuclei. A phase diagram in terms of the deformation parameter and angular momentum is given.